Mr. Yariiell on the Organs of Voice in Birds. 307 



uses to which the two processes already described are sub- 

 servient, and the action and effect of the muscles attached to 

 them, render it difficult for me to speak of them under any 

 better designation. 



The tube of the windpipe is composed of two membranes, 

 inclosing between them numerous cartilaginous or bony rings, 

 forming a cylinder more or less perfect from end to end. Ossi- 

 fication appears to commence in these rings at the front of the 

 trachea, from which point the bone gradually extends equally 

 on both sides towards the oesophagus as the bird increases in 

 age : in particular parts, however, of the tracheae of some birds 

 the rings are not entirely complete at any age. Various in- 

 equalities of size occur in different parts of the same tube in 

 some species, producing, as might be expected, a particular 

 efliect on the voice, to be hereafter explained ; and the length 

 of the tube deserves consideration. Thus, shrill notes are pro- 

 duced by short tubes, and vice versd ; the first are possessed by 

 the Singing Birds, and the reverse by the Waders and Swimmers; 

 but the diameter of the tube has also its influence, large tubes 

 producing notes low in the scale, and vice versd. The substance 

 of the tube itself has also to be considered, though some ano- 

 malies present themselves. Those birds possessing strong and 

 broad cartilages or bony rings have monotonous and loud voices, 

 while the more slender rings with enlarged spaces between them 

 allow a freedom of motion producing a corresponding variety in 

 the scale of tone. 



The inferior larynx, the true situation of the organ of voice in 

 birds, — as the experiments of Baron Cuvier have sufficiently 

 proved, — is situated at the bottom of the tube, and is formed 

 sometimes by the approximation of several of the lower rings of 

 the trachea more or less firmly ossified together, and occasion- 

 ally of solid bones ; varying in form, being compressed, coni- 

 cal, 



